1. Field of the Invention
The present invention relates to an antenna apparatus and a portable radio gear using the same, and more particularly, to an antenna apparatus provided with a radiative conductor and a portable radio gear using the same.
2. Description of the Related Art
Monopole antennas and loop antennas have been conventionally used for portable radio gears such as a portable telephone and a pager. As a portable radio gear has been made compact, an antenna is required to be made compact. Since a monopole antenna and a loop antenna need to have a radiative conductor with a length of one-fourth the wavelength of the used signal, however, the antennas become large and a demand for compact antennas cannot be satisfied.
To solve this drawback, the applicant has proposed a chip antenna, such as that shown in FIG. 12, in the Japanese Unexamined Patent Publication No. 8-316725. A chip antenna 50 is provided with a rectangular-parallelepiped base member 51 having a mounting surface 511 and made from dielectric ceramic including barium oxide, aluminum oxide, and silica as its main components. Inside the base member 51, a spirally wound conductor 52 is formed. A power-supply electrode 53 for applying a voltage to the conductor 52 is formed on surfaces of the base member 51. One end of the conductor 52 is drawn to a surface of the base member 51 and connected to the power-supply electrode 53. The other end of the conductor 52 forms a free end 54 inside the base member 51.
When a compact chip antenna having a low resonant frequency is produced with the use of the above conventional chip antenna, however, since a conductor for transmitting and receiving a radio wave is short, the gain and bandwidth are reduced.